This invention relates to a cutter knife comprising a band-shaped blade and a holder for holding the blade and used under such condition that one portion of the blade is projected for a required length from the front end of the holder and that if the cutting ability of the used portion of the blade is reduced, the front end portion thereof is broken off and then the blade if forwardly moved so as to use the succeeding portion of the blade.
In such kind of cutter blade, if the cutting ability of the used portion of the blade is reduced, the front end thereof is broken off and then the succeeding portion is required to be forwardly moved for the purpose of projecting this portion from the front end of the holder. As a result, it is indispensable to provide a holder for holding the blade so as to make it movable in its lengthwise direction, an operating member movable together with the blade with respect to the holder and a mechanism for securing both the blade and the operating member at any desired position to the holder.
In such kind of cutter knife, it has been proposed to use a click mechanism. Such conventional click mechanism, however, has the disadvantage that there is a risk of the blade being carelessly rearwardly moved when the blade is subjected to the force acting in a direction which is in parallel with the direction of movement of the blade.
It has also been proposed to use a screw threadedly engaged with the operating member and the front end of the screw is urged against the holder so as to secure the operating member to the holder. Such cutter knife has the drawback that the holder is required to have a sufficiently large mechanical strength, so that the holder must be formed of metal only and hence the cost of the cutter knife becomes expensive.